1. Field of the Invention
This invention relates to sheet feeding apparatus and more particularly to a registration mechanism for an apparatus for sheets fed seriatim.
2. Description of the Prior Art
In certain types of high speed reproduction equipment such as printing presses and electrophotographic copying machines, it has been a general practice to make copies on individual sheets of material. This eliminates the time (and aparatus) needed to process a web into cut sheets of desired size. The individual sheets are fed from a hopper seriatim along a delivery path to a printing plate bearing an ink or toner image. Since the plate may be moving relative to the path of the cut sheets, the movement of the sheets must be coordinated with the movement of the plate to insure registration of a sheet with an image to be copied. A registration mechanism, provided in the delivery path, typically includes a member which intercepts the delivery path and is contacted by the individual sheets as they are fed seriatim from the hopper. The member, which may be, for example, a gate or a roller, will stop the sheets (or at least slow the movement thereof) for the purpose of alignment, and then at a proper time release the sheets to be fed to the printing plate in registration with the image thereon. To enable the reproduction equipment to operate at high speed, a continuously operating drive moves the sheets into contact with the registration mechanism at a speed greater than the timed speed of movement necessary for the sheet to have proper registration with the image to be copied. This may cause the sheets to buckle, which in turn effects the degree of accuracy of registration in that upon release by the registration mechanism, the sheets will have variable spring-out forces induced by the buckle.